Method for detecting pungent odor from air conditioner, reproducing pungent odor and preparing corresponding pungent composition

ABSTRACT

Disclosed herein is a method for identifying the compounds contributing to a pungent odor from an air conditioner, a method for artificially reproducing the pungent odor, and preparing a corresponding pungent odor composition. Through the analysis method of the present invention, the compounds contributing to the pungent odor from an air conditioner may be identified and quantified. The pungent odor may be reproduced from a combination of the compounds identified by the analysis method of the present invention. The reproduced pungent odor may provide significant data required for development of an apparatus and a method for removing specific odors.

CROSS-REFERENCE

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2012-0092858, filed on Aug. 24, 2012, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for detecting a combination of compounds contributing to pungent odor from an air conditioner, a method for reproducing the pungent odor, and preparing a corresponding pungent composition.

2. Description of the Related Art

Clean air is regarded as an essential element for human health and well-being. Two important factors that lead to unsatisfactory indoor air quality in an airtight building are: the building itself producing a substantial amount of air pollutants that need to be removed or diluted; and odor generated as a result of human activities.

An air-cooling system lowers interior temperature and optimizes interior environment through air conditioning which changes air temperature, humidity, flow and cleanliness to more favorable conditions. Increasingly, air-cooling systems are being used to improve the standard of living. Although the air-cooling systems have been improved functionally over time, problems remain to be solved in terms of interior air quality. In the past, lowering interior temperature was viewed as one of the most fundamental and important functions of the air-cooling system. However, currently, health-related aspects such as interior air quality and odor may also be regarded as important functions of air-cooling systems. In particular, complaints regarding interior air quality include offensive odor such as pungent, foul odor, foot odor, and the like. To solve the odor problem, it may be necessary to analyze the odor-causing substances and understand the fundamental cause of the odor.

Although it is known that metabolites produced by fungi and bacteria are the cause of odor from an air conditioner, it may not be known what metabolites are produced and in what amount by the fungi and bacteria. Additionally, since it is unclear specifically what compounds cause the offensive odor, it may be necessary to understand the type of compounds which contribute to the pungent from the air conditioner.

SUMMARY OF THE INVENTION

Numerous complaints are commonly made regarding various offensive odors from an air conditioner (e.g., more than 20 kinds including musty odor). The present invention discloses a method for identifying the compounds contributing to the pungent odor from an air conditioner, collecting offensive-smelling gas from an automobile, and developing a method for artificially reproducing the pungent odor. The present invention provides a method for detecting the compounds contributing to pungent odor from an air conditioner from among various offensive odors emitted from the air conditioner.

The present invention also discloses a method for identifying the compounds contributing to pungent odor from an air conditioner from among various offensive odors emitted from the air conditioner and artificially reproducing the pungent odor using the identified chemical compounds. Additionally, the present invention also discloses a method of preparing a corresponding pungent odor composition from the detected pungent odor. The pungent composition may also be applicable to any applications where pungent odor is emitted, in addition to the air conditioner.

In one embodiment, the present invention provides a pungent odor composition from an air conditioner comprising one or more compounds selected from the group consisting of acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

In another embodiment, the present invention provides a pungent odor composition from an air conditioner comprising acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

In yet another embodiment, the present invention provides a method for analyzing the compounds contributing to pungent odor from an air conditioner, including the steps of (i) collecting a gas emitted from an air conditioner and (ii) analyzing the components of the gas.

In another aspect, the present invention provides a method for preparing a pungent odor composition from an air conditioner, comprising mixing two or more compounds selected from the group consisting of acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

Other features and aspects of the present invention will be apparent from the following detailed description and the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the present invention will now be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing which are given hereinbelow by way of illustration only, and thus are not limitative of the invention, and wherein:

FIG. 1 is an exemplary flow chart describing a method for analyzing the compounds contributing to pungent odor, according to an exemplary embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, reference will be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the accompanying claims.

In one embodiment, the present invention provides a detected pungent odor composition from an air conditioner comprising one or more compounds selected from the group consisting of acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone. More specifically, the present invention discloses a detected pungent odor composition from an air conditioner comprising acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

The detected pungent odor composition from an air conditioner may include:

0.0006-0.1 ppm of acetaldehyde;

0.0001-0.1 ppm of propionaldehyde;

0.0003-0.004 ppm of n-butyraldehyde;

0.01-30 ppm of toluene;

0.001-2 ppm of xylene; and

0.007-7 ppm of methyl ethyl ketone.

In an exemplary embodiment of the present invention, the pungent odor composition may further comprise one or more compounds selected from the group consisting of ethylhexanol, benzothiazole, N-phenylbenzenamine and 2-phenyl-2-propanol.

Specifically, the composition may further include:

0.0011-0.13 ppm of ethylhexanol;

0.0002-0.31 ppm of benzothiazole; and

0.0001-0.21 ppm of N-phenylbenzenamine

In another embodiment, the present invention provides a method for analyzing the compounds contributing to pungent odor from an air conditioner. The method includes the steps of (i) collecting a gas emitted from an air conditioner and (ii) analyzing the components of the gas.

In another aspect, the present invention provides a method for analyzing the compounds contributing to pungent odor from an air conditioner and reproducing the pungent odor. The method includes the steps of: evaluating offensive odor; collecting a gas emitted from an air conditioner; analyzing the components of the collected gas; classifying the components; reproducing compositions; performing a multiple test (e.g., for at least 5 panelists); selecting the representative composition; and completing the reproduction of the pungent odor composition.

FIG. 1 is an exemplary flow chart describing the method for analyzing the compounds contributing to pungent odor and reproducing the pungent odor.

The pungent odor of the present invention may be from an air conditioner in any environment including building, automobile, van, bus, etc. More specifically, the air conditioner may be an air conditioner used in an automobile, van or bus.

In an exemplary embodiment of the present invention, the gas in step (ii) may comprise acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone. The concentration of the acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone that contribute to the pungent odor may be measured. Additionally, the concentration of one or more compounds selected from the group consisting of ethylhexanol, benzothiazole, N-phenylbenzenamine and 2-phenyl-2-propanol may be measured. The analysis of the components in the step (ii) may be performed by gas chromatography/mass spectrometry (GC/MS), gas chromatography with atomic emission detector (GC/AED), gas chromatography/flame ionization detection/olfactometry (GC/FID/olfactometry) or high-performance liquid chromatography (HPLC), but is not limited thereto.

Representative examples of the analysis method of the present invention are described hereinbelow. However, the analysis method of the present invention is not limited thereto.

Gas Chromatography

In gas-solid chromatography (GSC), an adsorbent solid powder may be used as the stationary phase. In addition, in gas-liquid chromatography (GLC), a liquid stationary phase coated on a solid support may be used.

A carrier gas maintained at a constant flow rate may be supplied from a sample injection device into a separation column via a pretreatment apparatus and is discharged after passing through a detector. The pretreatment apparatus, the sample injection device, the column and the detector may be maintained at required temperatures.

When a gas or a liquid are introduced into the sample injection device, the gas may be carried into the column by the carrier gas and the liquid may be carried into the column by the carrier gas after being heated and evaporated. The components of the sample may be separated in the separation column based on difference in absorption or solubility and may sequentially pass through a mass analyzer disposed at the outlet of the separation column

The time between the injection of the sample into the separation column and a peak occurrence as a result of detection of a specific component included therein may be called retention time, and the retention time multiplied by the flow rate of the carrier gas may be called retention volume. Qualitative analysis may be performed on the process since the values of the retention time and volume may be different for different components under given experimental conditions. Furthermore, quantitative analysis may be conducted since the peak area or height may be related to the amount of the corresponding component present.

Electron ionization is a conventionally used ionization technique. Neutral sample molecules in gas state are bombarded with high-speed electrons to detach electrons and form molecular ions (cations, M⁺). The minimum energy required to produce the molecular ion (M+) from the neutral molecule (M) may be called ionization energy (IE). The ionization energy of an organic compound is 8-12 eV (800-1200 kJ/mol⁻¹). M+e ⁻→M⁺+2e ⁻

Among the produced molecular ions, those with high internal energy may be fragmented to form fragment ions.

To prevent ion formation owing to reaction between the produced ion and the neutral molecule, the pressure inside the ionization source should be maintained at 10⁻⁵ torr or lower.

Electron beams produced from a filament may be accelerated to 70 eV to obtain standard mass spectrums since they provide high ionization efficiency and little change in mass spectrum. The mass spectrum is the recording of the mass-to-charge ratio (m/z) of the molecular ions and the fragment ions. The mass spectrum of the unknown sample may be compared with the stored standard mass spectrums to identify the substance.

Electric fields and magnetic fields may be utilized alone or in combination to separate the ions according to their mass-to-charge ratio. A sector field analyzer, a quadruple mass analyzer, an ion trap, a time-of-flight, and the like may be used as a mass analyzer.

High-Performance Liquid Chromatography (HPLC)

The HPLC method may be utilized to separate nonvolatile substances which may be difficult to analyze by gas chromatography based on their difference in physicochemical interactions with a stationary phase and a liquid mobile phase. This method may be used for qualitative and quantitative analysis of aldehydes in the air. Additionally, in HPLC, the target substances may be separated in the separation column based on their difference in reactivity with the stationary phase and the mobile phase.

When HPLC is employed for analysis of aldehydes existing in the air, a separation column in which a nonpolar stationary phase is chemically bonded to a support may be used. Separation may be achieved depending on difference in reactivity and solubility for the mobile phase and the stationary phase. In general, the method wherein a column containing a nonpolar stationary phase is used and a relatively polar sample eluent is used to separate target substances may be called reversed-phase HPLC.

The material of the tubing in the HPLC method may be stainless steel, polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), glass, or a similar material. Generally, stainless steel may be preferable. Stainless steel may be advantageous due to being resistant to oxidation and corrosion. However, acid may cause damage and contamination to the tubing. Thus, when stainless steel is used, the tubing should be washed with distilled water after use.

Most often, an HPLC detector capable of measuring absorption in the UV-visible region may be used. When incident light of a particular wavelength is emitted from a light source on the sample in the cell of the UV-visible detector, it may be absorbed by the sample. The detector may generate an electrical signal corresponding to the light absorbance, thus allowing quantitative analysis of the sample.

Hereinafter, the method for detecting the components contributing to pungent according to the present invention is described. However, the application of the method is not limited to the described components.

Detection of Ammonia

The concentration of ammonia in the air may be measured as follows. After adding a phenol-sodium nitroprusside solution and a sodium hypochlorite solution to a sample solution to be analyzed, ammonia may be analyzed by measuring absorbance of indophenols formed from reaction with ammonium ion.

Detection of Methyl Mercaptan, Hydrogen Sulfide, Dimethyl Sulfide and Dimethyl Disulfide

The concentration of the sulfur compounds in the air may be measured as follows. After sampling using a sample bag, analysis may be carried out by cold trap-capillary GC and cold trap-packed column GC.

Cold Trap-Capillary GC and Cold Trap-Packed Column GC

The sulfur compound sample collected in the sample bag may be concentrated in a cold trap device, which may be maintained at −183° C. or below using a refrigerant and may be analyzed by GC after desorption. The measurement procedure may consist of sampling, concentration and sample injection to the separation column. A flame photometric detector (FPD), a pulsed flame photometric detector (PFPD), an atomic emission detector (AED), a sulfur chemiluminescence detector (SCD), a mass spectrometer (MS), and the like, capable of selectively detecting trace amount of sulfur compounds with substantially good linearity may be used as a detector.

Electronic Device Cooling Cold Trap-Capillary GC

Sulfur compounds existing in the sample may be concentrated at low temperature using a cold trap, desorbed at moderate temperature, and transferred into a syringe pump by the pressure of a carrier gas. The desorption may occur at moderate-to-low temperatures (e.g., 100° C. or lower). The concentrated sample transferred to the syringe pump may be injected into the separation column and analyzed by the detector. The cold-trapped sample may also be thermally desorbed and injected into the separation column.

Detection of Triethylamine

The concentration of triethylamine in the air may be measured as follows. After sampling using an impinger and acidic filter paper, analysis may be carried out by cold trap-packed column GC and headspace-capillary column GC.

Detection of Acetaldehyde, Propionaldehyde, Butyraldehyde, N-Valeraldehyde and Isovaleraldehyde

For simultaneous measurement of the concentration of acetaldehyde, propionaldehyde, butyraldehyde, n-valeraldehyde and isovaleraldehyde contributing to offensive odor, 2,4-dinitrophenylhydrazone (DNPH) derivatives of the aldehyde compounds may be formed and analyzed by HPLC and GC.

Dinitrophenylhydraziner (DNPH) Derivatization and HPLC/UV

DNPH derivatives formed by reacting the carbonyl compounds with 2,4-DNPH may be extracted with an acetonitrile solvent and analyzed by HPLC using a UV detector at 360 nm wavelength.

DNPH Derivatization and GC

DNPH derivatives formed by reacting the carbonyl compounds with 2,4-dinitrophenylhydrazine (DNPH) may be extracted with an acetonitrile solvent and analyzed by GC after changing the solvent to ethyl acetate.

HPLC Equipment

The HPLC equipment for sample analysis may include the following: the instrument which may consist of a sample injection device, a pump, a separation column and a detector (UV detector). The separation column may be a reversed-phase column (ODS column) having a nonpolar adsorbent coating allowing control of the mobile phase solvent according to the mixing ratio. The sample loop of the injection device may be 20-100 μL depending on the sample concentration.

GC Instruments

A capillary separation column may be used for GC, and a flame ionization detector (FID), a nitrogen phosphorus detector (NPD) or a mass spectrometer may be used as the detector.

Detection of Styrene

Styrene may be sampled at the site boundary. After sampling using a solid sorbent tube, a canister or a sample bag, analysis may be carried out by cold trap-GC and solid-phase microextraction (SPME)-GC.

Detection of Toluene, Xylene, Methyl Ethyl Ketone, Methyl Isobutyl Ketone, Butyl Acetate, Styrene and Isobutyl Alcohol

The concentration of toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, styrene, and isobutyl alcohol, which are volatile compounds contributing to offensive odors, in the air may be simultaneously measured as follows.

Toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, butyl acetate, styrene and isobutyl alcohol may be specified offensive odor substances. Sampling may be performed at the site boundary. The sample collected using a solid sorbent tube may be analyzed by GC after cold trapping and thermal desorption.

Detection of Propionic Acid, N-Butyric Acid, N-Valeric Acid and Isovaleric Acid

The concentration of the organic acids in the air may be measured as follows. After sampling using an alkaline-impregnated filter or by alkaline solution absorption, the collected sample may be pretreated by the headspace method to evaporate the organic acid components. Then, analysis may be carried out by GC.

In another embodiment, the present invention provides a method for preparing a detected pungent odor composition from an air conditioner, including mixing two or more compounds selected from the group consisting of acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

In another embodiment, the present invention provides a method for preparing a detected pungent odor composition from an air conditioner, including mixing acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone.

In yet another embodiment of the present invention, the method for preparing a detected pungent odor composition from an air conditioner may include mixing one or more compounds selected from the group consisting of ethylhexanol, benzothiazole, N-phenylbenzenamine and 2-phenyl-2-propanol.

In an exemplary embodiment of the present invention, the method for preparing a pungent composition from an air conditioner according to the present invention may include mixing:

0.0006-0.1 ppm of acetaldehyde;

0.0001-0.1 ppm of propionaldehyde;

0.0003-0.004 ppm of n-butyraldehyde;

0.01-30 ppm of toluene;

0.001-2 ppm of xylene; and

0.007-7 ppm of methyl ethyl ketone.

In another exemplary embodiment of the present invention, the method for preparing a pungent composition from an air conditioner according to the present invention may further include mixing:

0.0011-0.13 ppm of ethylhexanol;

0.0002-0.31 ppm of benzothiazole; and

0.0001-0.21 ppm of N-phenylbenzenamine

EXAMPLES

The present invention will be described in more detail through examples. The following examples are for illustrative purposes only and it will be apparent to those skilled in the art not that the scope of this invention is not limited by the examples.

Example 1 Sensory Test

1) Selection of Car Model

Odor was sampled from the air conditioner of a car model A.

2) Sensory Test Method

i) Three out of the four air conditioner exhausts were sealed hermetically.

ii) For sensory test and gas sampling, the exhaust at the left side of the driver's seat was sealed hermetically using a glass tube using a vinyl bag.

iii) The air conditioner was operated at level 2 under internal ventilation condition.

iv) The panelist was asked to smell the sample in the glass tube and evaluate the intensity and type of odor.

Table 1 describes the level of odor according to intensity used as the standard of sensory test and evaluation after preparation of the mixtures for reproducing the odor in Examples 3 and 4.

TABLE 1 Odor intensity Level of odor 5 Irritating and intense odor 4 Strong odor 3 Weak but easily perceivable odor 2 Perceived but slight odor 1 Almost unperceivable odor 0 No odor

Example 2 Sampling Procedure

1) Selection of Car Model

Sample was taken from the same car as in Example 1.

2) Sampling Method

i) Three out of the four air conditioner exhausts were sealed hermetically.

ii) The exhaust at the left side of the driver's seat was sealed hermetically using a glass tube using a vinyl bag.

iii) The opening of a 10-L PE sample bag was connected to the glass tube.

iv) The air conditioner was operated at level 2 under internal ventilation condition and gas sample was taken.

Example 3 Sample Analysis

The sample taken in Example 2 was analyzed by absorption spectrophotometry, headspace—gas chromatography with flame ionization detector (HS-GC/FID), gas chromatography with flame photometric detector (GC/FPD), high-pressure liquid chromatography with ultraviolet detector (HPLC/UV), gas chromatography/mass spectrometry (GC/MSD) and headspace-gas chromatography/mass spectrometry (HS-GC/MS).

Table 2 shows the result of detecting representative compounds contributing to offensive odor.

TABLE 2 Car model A Car model A Condition #1 Condition #2 Sensory test Characteristic Pungent Pungent Intensity 2-3 2-3 Analysis of specified Ammonia 5.88 0.82 offensive odor Methyl mercaptan ND ND substances (unit: Hydrogen sulfide ND ND ppm) Dimethyl sulfide ND 0.00011 Dimethyl disulfide ND ND Trimethylamine ND ND Acetaldehyde 0.00066 0.00080 Styrene ND ND Propionaldehyde 0.00012 0.00012 n-Butyraldehyde 0.00364 0.00357 n-Valeraldehyde ND ND Isovaleraldehyde ND ND Toluene 0.01741 0.02028 Xylene 0.00182 0.00288 Methyl ethyl ketone 0.00707 0.00706 1) Condition #1: Blower level 2 + air conditioner on for 5 minutes, GC analysis: 0.1 L/min, LC analysis: 1.0 L/min. 2) Condition #2: Blower level 2 + air conditioner off for 5 minutes, GC analysis: 0.1 L/min, LC analysis: 1.0 L/min.

Example 4 Preparation of Pungent Odor Composition

A pungent odor composition was prepared by mixing ammonia, acetaldehyde, propionaldehyde, n-butyraldehyde, toluene, xylene and methyl ethyl ketone among the components described in Table 2 and further mixing the additional components described in Table 3 (Condition #1) or Table 4 (Condition #2).

TABLE 3 Final Final concentration volume Temperature Pressure (ppm) (L) (° C.) (mb) Mass (μg) Ammonia 5.88 10 20 1013.25 0.041653571 Acetaldehyde 0.00066 10 20 1013.25 1.21306E−05 Propionaldehyde 0.00012 10 20 1013.25 2.99568E−06 n-Butyraldehyde 0.00364 10 20 1013.25 0.000109116 Toluene 0.01741 10 20 1013.25 0.000667262 Xylene 0.00182 10 20 1013.25 8.01962E−05 Methyl ethyl ketone 0.00707 10 20 1013.25 0.000212052 Additional components Ethylhexanol 0.01166 10 20 1013.25 0.000631859 Benzothiazole 0.02316 10 20 1013.25 0.001302259 N-Phenylbenzenamine 0.01384 10 20 1013.25 0.000974089 2-Phenyl-2-propanol 0.00732 10 20 1013.25 0.000414789

TABLE 4 Final Final concentration volume Temperature Pressure (ppm) (L) (° C.) (mb) Mass (μg) Ammonia 0.82 10 20 1013.25 0.005808831 Dimethyl sulfide 0.00011 10 20 1013.25 2.76549E−06 Acetaldehyde 0.00080 10 20 1013.25 1.45677E−05 Propionaldehyde 0.00012 10 20 1013.25 2.92321E−06 n-Butyraldehyde 0.00357 10 20 1013.25 0.000106986 Toluene 0.02028 10 20 1013.25 0.000777335 Xylene 0.00288 10 20 1013.25 0.000127183 Methyl ethyl ketone 0.00706 10 20 1013.25 0.000211633 Additional components Ethylhexanol 0.01299 10 20 1013.25 0.000703398 Benzothiazole 0.03166 10 20 1013.25 0.001780577 N-Phenylbenzenamine 0.02135 10 20 1013.25 0.001502865

The odor of the samples obtained from the air conditioner of the car model A under the conditions #1 and #2 was pungent odor of intensity 2-3, as described in Table 5.

The pungent odor composition prepared from a combination of the aforementioned components was also pungent odor of intensity 2-3, similar to that from the air conditioner.

TABLE 5 Car model A Car model A Condition #1 Condition #2 Odor from car Intensity 2-3 2-3 air conditioner Characteristic Pungent Pungent Pungent composition Intensity 2-3 2-3 prepared from Characteristic Pungent Pungent detected compounds Note Intensity Similar Characteristic Similar

The features and advantages of the present disclosure may be summarized as follows:

(i) Through the analysis method of the present invention, the compounds contributing to the detected pungent odor from an air conditioner may be identified and quantified;

(ii) The pungent odor may be reproduced from a combination of the compounds identified by the analysis method of the present invention; and

(iii) The reproduced pungent odor may provide significant data required for development of an apparatus and a method for removing specific odor.

The present invention has been described in detail with reference to specific embodiments thereof. However, it will be appreciated by those skilled in the art that various changes and modifications may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the accompanying claims and their equivalents. 

What is claimed is:
 1. A detected pungent odor composition from an air conditioner comprising: 0.0006-0.1 ppm of acetaldehyde; 0.0001-0.1 ppm of propionaldehyde; 0.0003-0.004 ppm of n-butyraldehyde; 0.01-30 ppm of toluene; 0.001-2 ppm of xylene; 0.007-7 ppm of methyl ethyl ketone, 0.0011-0.13 ppm of ethylhexanol; 0.0002-0.31 ppm of benzothiazole; and 0.0001-0.21 ppm of N-phenylbenzenamine.
 2. A method for preparing a detected pungent odor composition from an air conditioner, comprising: mixing 0.0006-0.1 ppm of acetaldehyde; 0.0001-0.1 ppm of propionaldehyde; 0.0003-0.004 ppm of n-butyraldehyde; 0.01-30 ppm of toluene; 0.001-2 ppm of xylene; 0.007-7 ppm of methyl ethyl ketone, 0.0011-0.13 ppm of ethylhexanol; 0.0002-0.31 ppm of benzothiazole; and 0.0001-0.21 ppm of N-phenylbenzenamine. 